I've never read or learned anything about feng shui (until I read this post!) but now I'm intrigued so I want to learn more (more for curiosity's sake than anything else).
Personally, I don't believe in the fish tank bringing upon you bad luck. For me, my fish tank is RIGHT NEXT to my bed. As in inches from it. It's 4 feet long, so it prettymuch dominates one side of my bed. And I love it there: it relaxes me, gives me something to watch when I'm bored and something to think about before I go to sleep, and is overall very soothing (especially with running water and animals - I'm a water sign, and maybe that has something to do with the attraction to water, but who knows).
About the growth in your breast: get it checked RIGHT AWAY. I cannot stress that enough! (The computer got mad, said I was yelling and not to use caps, but whatever!
) My grandmother died from cancer that started in her lymph nodes (near armpit) and spread to her lungs. The sooner that can be looked into, the better. I sincerely hope it is only a false alarm or something related to that, and I truly hope that your other illnesses go away. I think it has nothign to do with the fish tank - although my grandmother didn't do feng shui or have a fish tank. (Fish = relaxation!!!)
Best of luck all around, and remember no matter what, we are here for you! (Even if it means denouncing feng shui!